The present invention relates to a system for forming the shed in a seam weaving portion for joining the ends of a fabric and to a method of forming a woven seam using the system.
As known in the art, the ends of a fabric are joined together to form an endless fabric or the peripheral edge of a fabric is joined to that of another fabric to form a larger piece of fabric. In most of the conventional methods, the ends of the fabric or the peripheral edges are overlapped with each other and then sewn together or bonded together.
However, the above-mentioned conventional method of joining together fabric can not be employed for papermaking fabrics, such as a sheet forming fabric. This is because such papermaking fabrics require a uniform structure and a uniform filtration space. Otherwise, the resultant paper product formed on the fabric is nonuniform in thickness and causes undesirable marking to occur.
In addition, fabrics for use in the manufacture of nonwoven fabrics must have a uniform structure in view of touch, laminatability and uniformity.
Further, the above-mentioned conventional method can not be used for fabrics which are for covering the sludge in a pressure dewatering process. This is because leakage of the sludge occurs due to the presence of the nonuniform filtering area in adjoining ends of a fabric which face each other. A method of alleviating this problem includes removing transversal or weft threads in one of the joining ends over a seam width to leave longitudinal or warp threads alone, introducing the warp threads into a fabric structure of the other joining end, and cutting and removing parallel warp threads of the other joining end. However, this method is not practically available unless the fabric is a coarse mesh.
In this connection, it has been considered to join the ends of a fabric by weaving, in adjoining portions, a fabric which is similar in structure to the main body of the fabric.
According to this prior method, threads which serve as warp threads corresponding to weft threads of the main body of the fabric are separated vertically upwardly to form the shed in a seam weaving portion. On the other hand, threads in both ends of the fabric to be joined are introduced into the shed as weft threads. Thus, a woven seam is formed. However, in order to effectively and mechanically perform the shed formation for weaving, there exists no other means superior to the known Jacquard device.
However, the Jacquard device generally requires longitudinal needles, transverse needles, knives, pattern cards, cylinders for receiving the pattern cards and inevitably has a large size. It is therefore inappropriate to use the Jacquard device in forming a woven seam which is narrow.
In sheet forming fabric, a wide variety of fabric structures are used and multi-layer fabrics have recently been put into use. In this connection, the number of heddles inevitably increases. This results in a further increase the size of the shedding system. Thus, such a conventional shedding system is not satisfactory for use in a seam weaving operation.
In addition, the Jacquard device has heddles each of which is supported at both upper and lower ends thereof and moved for the shed formation. With this structure, it is impossible to separately pick up an individual one of the heddles. When a large number of the heddles are arranged in a seam weaving portion which is narrow, it is difficult to thread the heddles surrounded by a mass of heddle supporting members standing together closely. If a thread is snapped during the seam weaving operation, it is extremely difficult to find the particular heddle in question and to thread the particular heddle for recovery.
In particular, the Jacquard device encounters difficulty in treating multi-layer fabrics, such as double-layer fabrics and triple-layer fabrics, which have recently been put into use.
As is known in the art the term "shed" means the path through and perpendicular to the warp in a loom. The shed is formed by raising some warp threads by means of their harness while others are left down. The shuttle press through the shed to insert the filling. The term "shedding" means the operation of forming a shed in the weaving process. Also as is known in the textile art, the heddle is a cord, round steel wire, or thin flat steel strip, or equivalent with a loop or eye near the center through which one or more warp threads pass on the loom so that their movement may be controlled in weaving. The heddles conventionally are held at both ends by the harness frame. They control the weave pattern and shed as the harnesses are raised and lowered during weaving.
As a result of a study to overcome the above-mentioned disadvantages, it was determined that a shedding system must be modified in order to improve the seam weaving speed and to form a woven seam of a wide variety of fabric structures.